Relaxing the half-wavelength condition for estimating signal AOA at a line of sensors

This paper introduces an estimation technique for the angle of arrival (AOA) of incident signal on a line of sensors from the differences of the signal phases at different sensors. Unlike known techniques, the distances separating neighbouring sensors may exceed half the wavelength `lambda´ of the incident signal. The proposed technique assumes estimating the continuous frequency (in rad/sec) and the phase of the sinusoids in the signal at each sensor in a previous step. Knowing the continuous frequency, and consequently the wavelength, it becomes possible to detect the occurrence of multiple complete wave cycles between sensors, thus relaxing the half-wavelength condition. To be able to detect multiple cycles, the technique assumes one of two conditions: 1- the signal contains at least two frequencies, and if not 2- there are at least three unequally spaced sensors. A maximum limit, greater than half the wavelength, is derived for the sensors spacing while still being able to resolve the ambiguity caused by the possibility of multiple cycles. Numerical results show good statistical behaviour of the technique.